FDA Commissioner Scott Gottlieb, who has called teen use of e-cigarettes an "epidemic," has been critical of Juul and other companies, arguing that marketing is aimed at youth by labeling e-liquids to resemble "kid-friendly" foods like juice boxes, candy and cookies.

Flavors that taste like fruit and candy are the most popular with teenagers and also account for the majority of Juul’s sales.

The FDA says e-cigarettes may be an alternative for adults trying to transition away from traditional tobacco products, like cigarettes.

At the same time, Gottlieb has hinted at future regulatory actions, writing last month that "the FDA won’t tolerate a whole generation of young people becoming addicted to nicotine as a tradeoff for enabling adults to have unfettered access to these same products."

The FDA conducted a surprise inspection of Juul's corporate headquarters in September and collected more than a thousand pages of documents.

Potential regulatory actions include a possible ban on flavored e-liquids if five of the largest manufacturers can't come up with adequate plans to help keep e-cigarettes out of the hands of those under the age of 18.